1. Field of the Invention
The invention relates to a numerical controller for controlling an industrial machine such as a machine tool and a manufacturing machine, and in particular to a path-table operation, i.e. so-called electronic cam control in which axes of the machine are controlled to be synchronized by the numerical controller.
2. Description of Related Art
As a method of drivingly controlling axes of a machine in synchronism with motion of a reference axis, there is known a path-table operation, i.e. so called “electronic cam control”, in which each of the controlled axes is driven in synchronism with the reference axis based on a path-table operation data table storing information on command positions of controlled axes with respect to positions of the reference axis, from Japanese Laid-Open Patent Publication Hei 3-296109, for instance. A spindle or an external axis of a machine tool is designated as the reference axis, and a present position of the reference axis is determined based on a pulse signal from a position coder provided at the spindle or an external pulse signal from the external axis. The synchronized operation of the controlled axes with the reference axis is performed by determining a command position of each of the controlled axes for the present position of the reference axis based on the information on command position of the controlled axis for the position of the reference axis stored in the path-table operation data table prepared for each controlled axis, and driving each of the controlled axes to the command position.
In the above-mentioned conventional path-table operation (electronic cam control), the speed of each controlled axis is fixedly determined in accordance with the rotating speed of the reference axis, and cannot be altered. However, in general, prior to actual machining with the machine tool, motions of the axes are checked with the spindle as the reference axis not connected to a workpiece to be idle, and increasing or decreasing feed rates of controlled axes of an X-axis and a Z-axis. Further, under some machining conditions, the feed rates of controlled axes may be changed even during actual machining.
Also, in the pass-table operation (electronic cam control), it is desirable that the speed of controlled axes is changeable as mentioned above. However, conventionally, the speed of controlled axes depends on the speed of a spindle (reference axis) and cannot be changed.
Further, generally, a machine tool has auxiliary functions such as starting or stopping supply of cutting fluid, and spindle functions such as changing the rotating speed of the spindle, etc., and is operated using those auxiliary functions and spindle functions. However, in the conventional path-table operation (electronic cam control), the auxiliary functions and spindle functions cannot be used to be inconvenient for users.
Further, in the conventional path table operation (electronic cam control), it is inconvenient that data in a path-table operation data table are required to be changed when a tool wears.
Furthermore, it is inconvenient that relative position of the reference axis and the controlled axes need to be determined on the basis of a fixed position, and respective positions of start of the path-table operation of the controlled axes need to be determined on the basis of the fixed position in advance.